Large thermoelastic effect in <b> <i>α</i> ″ </b> martensite of TiZrNbSn

Abstract

Highly reversible elastic deformation endows the associated thermoelastic effect with considerable potential for solid-state cooling. In this work, we report a large adiabatic temperature change (ΔTad) in a TiZrNbSn alloy with α″ martensite. To enhance ΔTad, a microstructure optimization strategy based on broadening single-variant martensite domains via compressive preloading is implemented. Unlike the stress-free, self-accommodated martensitic state, stress-induced detwinning promotes a single-variant state in which the [100] orientation aligns with the compression direction. In this state, the lattice deforms cooperatively under stress, leading to a significantly enhanced thermoelastic response. Consequently, ΔTad increases progressively with higher preloading stress, reaching a value three times greater at 800 MPa than that of the non-preloaded sample. However, excessive preloading activates dislocation slip, which degrades the thermoelastic response. The alloy also exhibits a wide operating temperature range of 295–475 K, achieving a ΔTad of 2.0 K at 475 K. This work provides insights into the microstructure–property relationship governing the thermoelastic effect in martensitic alloys.